The interrelation between form and function in the developing cardiovascular system is largely unknown. Experiments with embryonic chick hearts have shown that perturbing ventricular pressure alters the rate of growth without affecting the rate of morphological development. These results suggest a biomechanical basis for growth, but the specific mechanism(s) is not yet known. The long-term goal of this research is to identify the biomechanical factor that regulates growth in the embryonic chick ventricle. Correlating experimental data with results given by a realistic theoretical model will facilitate meeting this goal. Hence, the specific aims of this project are: 1. Develop a series of theoretical models for the embryonic ventricle during the early stages of development from a muscle-wrapped tube into a four-chambered pump. Compute stress, strain, blood flow, and strain- energy density distributions in the ventricular wall using nonlinear shell theory and poroelasticity theory. 2. Measure the geometric and biomechanical properties of the embryonic chick heart by correlating theoretical results with data from material testing protocols. Determine how these properties change with development and perturbed loading conditions. 3. Validate the model by comparing theoretical predictions with measured epicardial wall strains and blood-flow distributions through the wall of the embryonic chick heart. 4. Use the model to study the effects of various material and geometric parameters on stress, strain, blood flow, and strain-energy density distributions in the ventricular wall. 5. Correlate experimental and theoretical results to normal growth patterns from experiments that alter normal cardiac loadings. Identify the biomechanical factor(s) that regulates heart development. Supporting biologic studies of function and growth, the theoretical model will promote and understanding of the biomechanical principles responsible for normal and abnormal cardiac development.